1. Field of the Invention
This invention relates generally to fastener driving guns, and more particularly to a gun capable of using explosive cartridges mounted in a strip-type magazine.
2. Description of the Prior Art
Fastener driving guns are widely used to drive fasteners such as nails, studs or the like into hard materials such as metals or concrete, usually to serve as anchors for something to be attached to the hard material. An example of such a gun is shown in U.S. Pat. No. 3,066,302, issued to DeCaro et al. on Dec. 4, 1962. The gun disclosed in that patent would handle a single cartridge at a time. More recently, guns have been developed which can handle a band or strip of cartridges. Examples are shown in U.S. Pat. No. 3,552,625 issued to Udert on Jan. 5, 1971, and U.S. Pat. No. 3,554,425 issued to Oesterle on Jan. 12, 1971. Those patents show different arrangements for supporting the back of the cartridge magazine strip.
It has been found that, after firing a cartridge, it is desirable to retract the firing pin slightly, to avoid interference with movement of the cartridge shell, and shell magazine strip through the gun to move the next cartridge into position to be fired. Heretofore, a spring has been used to retract the pin. Some difficulties with this approach are the abuse that the pin retract spring receives during the firing of the gun, some resistance to the action of the firing pin and the pin driving spring due to the opposing force of the retracting spring, the necessity of relying on a spring of relatively low spring force for the retraction function, and the possible impedance of its proper function due to corrosive or fouling effects of the combustion products of the explosive cartridges.
In addition to the firing pin retraction aspect of prior art guns, I have observed that at least some of them return the trigger to the ready position without necessarily returning the sear release mechanism to the ready position. The present invention is directed to elimination of the firing pin return spring and providing a positive return of the sear release linkage along with the trigger.